View Article Online / Journal Homepage / Table of Contents for this issue 91 XII1.-On some Leadhills Minerals. By NORMANCOLLIE, Ph.D., F.R.S.E. THE Leadhills in the south of Scotland has long been known as a locality from which many interesting minerals can be obtained. Some seemingly are peculiar to the Leadhills district, viz., susanite, a double sulphate and carbonate of lead ; and caledonite, a basic sul- phate of lead cont.aining copper and carbonic acid ; whilst others, viz., leadhillite, a mineral similar in composition to susanite ; lanark- ite, a basic sulphate of lead ; vanadinite and plwmbo-calcite are met with only in one or two other localities. Most of the minerals, the analyses of which are given in this paper, I obtained myself some years ago at Leadhills, the remainder* were collected by Dr. Wilson, of Wanlockhead, Leadhills. These I have from time to time analysed, with results which I have now collected in the following paper. I have also incorporated several analyses made by Mr. Wheeler, at the Queen’s College, Belfast. Two minerals amoiigst those which I have analysed do not seem to have been pre- viously noticed. (1.) Plumbo-aragonite, or aragonite containing lead carbonate. (2.) Calcium unnado-pyromorphite, or pyromorphite containing calcium and vanadic acid, with a small quantity of copper hydroxide. The investigation of these Leadhills minerals was undertaken for several reasons, the chief being to ascertain whether in the large Published on 01 January 1889. Downloaded by University of Windsor 27/10/2014 13:39:51. number of double carbonates, sulphates, phosphates, &c., found there, the constituent salts were present in any simple molecular propor- tion; another being to determine which analyses amongst the con- flicting ones met with in mineralogical treatises are the most probably correct. Leadhillite. This substance is not often found at Leadhills, and for several years past, few new specimens have been obtained. It occurs also as maxite in Sardinia. The earlier analyses given differ considerably from the later ones. At one time it was considered to be a mixture of sulphate and carbonate of lead in the proportions PbC03,3PbSOa. This, however, is obviously incorrect, for not only does the substance contain from 1 to 2 per cent. of water, but there is an insufficient * These minerals were first given to Professor Letts of Belfast, who afterwards kindly handed them over to me for analysis. H2 View Article Online 92 COLLIE ON SOME LEADHILLS MINERALS. amount of sulphuric and carbonic acids to combine with the whole of the oxide of lead. If the earlier analyses are omitted, the carbonic acid is found to vary from 8.5-12.1 per cent., as the following analyses will show :- Calculated for I. IT. PPbS04,2PbCOs,Pb(0 a),. PbO.. ...... 80-7 80.8 80.7 co,.. ...... 12.1 9.2 9.1 SO3 ........ 7.1 8.2 8.3 HZO.. ...... - 2.0 1.8 No. I is an analysis by 13ertrand (Bull. SOC.China., Paris, 1873). No. I1 is by Hintze (Pogg. Ann., 152, 356). Three separate specimens of leadhillite were ctnalysed, and it was found that the amount of carbonic and sulphuric acids varied con- siderably. I. r--L-- 7 (..) (6.) b) IT. 111. PbO.. .... 82.5 82.3 82.1 82.8 81.3 CO,...... 8.6 8.5 8.7 9.8 11.5 SO3 ...... 9.1 9.2 9-2 8.0 7.3 H,O.. .... 1.5 1.6 1.5 1.6 1.8 These results seem to point to the fact that leadhillite varies in com- position, the ratio between the sulphate and carbonate of lead not remaining constant. Lanarkite. This mineral is stated by Brooke and Thomson to be a compound having the formula PbSO,,PbCO, ; but subsequent analyses by Published on 01 January 1889. Downloaded by University of Windsor 27/10/2014 13:39:51. Pisani and by Flight show that it does not contaiii carbonic acid, aud this is corroborated by the following analyses III (a) and (b). 111. ---T Calculated for I. 11. (a). (b.) PbSO,,PbO. PbSO, ........ 57.2 57 7 57.8 37.5 57.6 PbO .......... 40.6 42.9 41.4 41.8 42.4 Loss on ignition 0.81 - 0.5 0.5 - No. 1, Pisani (Compt. reml., 1873). No. IT, Flight (this Journal, 1874, 103). Lannrkite, therefore, unlike leadliillite, seems to be of constant com- position. Caledonite. Caledonite is one of the rarest of the Leadhills minerals, and is not View Article Online COLLIE ON SOME LEADHILLS MINERALS. 93 often met with. The few analyses given of it differ very considerably, the earlier ones of Brooke and Thomson giving 31-9-32.8 per cent. of lead carbonate, while Maskelyne and Flight (this Journal, 1874, 191) find only traces of carbonic acid. Flight and Maskel~ne. f--- f--- 7 Found. Mean of I. 11. two analyses. PbSOa.. .... 60.2 59.5 59-1 PbO ....... 25.1 26-2 24.2 CUO ........ 9.4 9.2 10.7 CO, ........ 1.4 - 1.9 H,O ........ - 3-7 3.5 These percentages do not agree with any simple formula, and caledonite may be a hydrated form of lanarkite, in which the hydrate OE lead has been replaced by a variable amount of copper hydrate. Linarite. This magnificent mineral is met with at Leadhills, but fine specimens also occur in Cumberland and elsewhere. It does not Seem ever to contain carbonic acid, and the analyses agree well with the formula P bS04,Cu0,H20. Found. Mean of Calculated for 1. 11. two analyses. PbS04,Cu0,H20. PbSOd .. 75.4 74.8 75.3 75.6 CuO.. .. 18.0 19.7 7 9.6 19.8 H20.... 4.7 5.5 5.2 4.5 Pyromorphite. Published on 01 January 1889. Downloaded by University of Windsor 27/10/2014 13:39:51. The specimens of this mineral which are found at Leadhills are remarkable for their great beauty of colour, which varies from the richest orange to light or dark olive-green. The brilliant orange variety has been supposed to contain chromium, and is sometimes called chromophosphate of lead, but there are no analyses of any pyromorphite from Leadhills containing even a trace of that metal. Another variety of pyromorphite often found is light green in colour, and in botryoidal masses with a conchoidal fracture; this seems peculiar to Leadhills, and might possibly be mistaken for calamine. Various differently coloured pyromorphites were andysed :- Ca.lculated for Orange. Green. Yellow. 3Pb3(PO4).,,PbCl2. PbO ...... 81-4 - 81.6 81.7 Pz06...... 15.7 15.9 15.9 15.6 CI, ....... 2.6 2-6 2.8 2.6 View Article Online 94 COLLIE ON SOME LEADELILLS MINERALS. Arsenic acid was only present in extremely small quantity. Several experiments were also made to determine whether the green colour was due to an appreciable amount of a ferrous salt, but without success ; traces of iron were present, but always seemed to be in the ferric state. From the above analyses, the pyromorphites seem to differ but little in composition. Vanadhit e. Although this mineral contains the rare element vanadium, still it has been found in various other localities besides Leadhills. It is seldom found at Leadhills in the crystalline condition, usually occurring as a deposit on calamine in the form of small granules. Two different specimens were analysed :- Calculated for I. 11. 3Pb3 (YO,) e,Pb Clp PbO .......... 80.0 79.6 78.2 VzO5 .......... 16.7 16.2 19.3 C1 ............ 2.5 2.4 2.5 H20 .......... 1.2 1.4 - Various specimens were tested for phosphoric acid and also for chromium, but neither of these substances was present. Calcium Yanado-pyromorphite. This new mineral occurs in black botrjoidd masses, and is unlike either pyromorphite or vanadinite in appearance, The frac- ture is uneven or conchoidal; it fuses easily before the blowpipe, leaving a brown granule, which when broken shows a, crystalline Published on 01 January 1889. Downloaded by University of Windsor 27/10/2014 13:39:51. structure. It dissolves readily in hydrochloric acid when warm, and leaves a slight residue of a brown colour, which consists chiefly of ail oxide of iron. Two analyses were made :- Ratios between the phos- phates, vanadates, and the lead chloride in I. IT. analysis No. I. Pbs(PO,), ........ 52.0 - 0.0641 PbS(V04)z ........ 19.2 - 0.0224 3.3 Ca3(POA)z........ 15.8 - 0.0510 PbClz.. .......... 11.4 10.7 0.0410 I 1.0 Cu(OH), ........ 1.6 1.4 Insoluble residue .. 0% 0.5 The specific gravity is 6.9-7.0. The mineral is therefore a pyromorphite in which calcium replaces View Article Online COLLIE ON SOME LEADHILLS MINERALS. 95 lead, and vanadic acid replaces phosphoric acid. The amount of water (0.4 per cent.) which the mineral loses wheE it is heated is just enough to combine with the oxide of copper, and as there is an insu6cient amount of acid to unite with all the bases present, this is rendered probable. Unfortunately there was only a, very small quantity of the mineral, so no further analyses could be made. Pturnbo-calcite. Most of the calcite which is found at Leadhills contains some lead carbonate. The transparent crystals contain the least, whilst the opaque and vitreous looking varieties contain sometimes as much as 9.5 per cent. The specific gravity does not vary much (2.7-2.8). Six different specimens were analysed, two determinations of lead being made in each case:- I. 11. 111. 'Iv. v. VI. PbCO, .......... 1.4 1.2 1.4 39 5.2 3-9 CaC03 (by diff.).